Colored cellulose azo compounds and their method of production



UNITED STATES PATENT OFFICE COLORED CELLUIDSE AZO COMPOUNDS AND THEIRBIETHOD 0F PRODUCTION Ralph Dinklage, New York, N. Y.

No Drawing. -Application December 16, 1935, Serial No. 54,725

icclaims.

Thisapplication is a continuation in part'of my prior-application,Serial Number 531,264, filed April 18, 1931.

The invention relates to new dyestufls containing a cellulose moleculein ether or ester combination with a dyestufi molecule, and to themethod of producing such dyestuffs.

A considerable number of dyestuils, though producing fine and highlydesirable shades,

possess the dlsadvantage'of not being fast to light. I have discoveredthat the fastness to light of dyestufis' may be greatly increased bycombining a cellulose molecule with a dyestufl' molecule in such mannerthat at least one of the reactive OH groups per glucose residue of thecellulose molecule is esterified or etherified with an aromaticcarbocyclic compound, the latter being a constituent part of themolecule structure 0 the dyestuil. K

The products obtained in accordance with the invention are of greaterstability, and possess a higher fastness to light than the corresponding dyestufi not coupled to a cellulose molecule, and due to the waterinsolubllity of the cellulose esters, or ethers .of this type, aconsiderable improvement in fastness to washing is obtained. The newdyestufls may be used very advantarials for varnishes, lacquers, and thelike, either dissolved in the varnish or lacquer, or incorporated in theform of a pigment.

In accordance with the invention a cellulose or cellulose derivativeesterified or etherified with an aromatic nitro-carbocyclic compound orderivative, is converted into the amino compound, which is thereafterdiazotized and subsequently coupled with a'suitable coupling agent. Suchcellulose nitro-esters or ethers that may be used for the production ofthe novel dyestufls, and possessing the afore-mentioned desirablecharacteristics, are represented by the following general formulae:

- in which Z represents a glucose residue of a cellulose molecule,R,.an-alkyl residue, in the case of higher alkyl homologues, they may beeither of straight or branched chain configuration, R

- a carbocyclic structure, m, the number of nitro groups carried by thecarbocyclic structure, while a: designates the number of OH groups soesterifled or etherifled per glucose residue of the cellulose molecule.It is understood that also mixed esters or ethers may be used, such ascellulose acetate-benzoate, nitro-benzoate, acetate-benzyl ether, ethylether-benzoate, etc., which are characterized by the general formulae: o

geously for dyeing and printing textile fibres or fabrics, whereby thedye bath or the printing paste, as the case may be, may comprise eithera solution or a suspension of the cellulose dyestuil'. These dyestuffsmay be used on animal as well as on vegetable fibres. In the case ofartiilcial fibres-produced by regenerating cellulose or cellulosederivatives from their solutions in a so-termed spinningprocess, it issometimes 'of advantage to add. a 'coloring material to the spinningsolution, and for this purpose my cellulose dyestuils are well suited.The new products may be also used successfully as coloring mater ys. andit is my belief that the increased fastness to light and the enhancedstability of the dyestuffs, made in accordance with my invention,

is substantially due to the enlargement of the dyestufi' moleculeobtained by its combination 5 with a cellulose molecule in theabove-described manner, whereby the new dyestufl becomes less sensitiveto the action of ultra-violet rays.

The following examples illustrate the method of carrying out myinvention without, however, limiting the same to the illustratedembodiments.

Example 1. parts by weight of finely cut cellulose p-nitro benzoic acidester are mixed with 80 parts by volume of a normal NaHS solution,whereupon the mixture is heated on a water bathof a temperature of 60 to70 C. for one hour with rigorous stirring. After filtering and thoroughwashing, the amino product possessing a yellowish appearance, is mixedwith 50 parts by volume of a diluted sulphuric acid (10 parts by volumeconcentrated H2SO4+50 parts by volume H2O), whereupon the mixture isheated on the water bath at a bath temperature of 70 C. for a period offrom to 30 minutes, preferably .with stirring. After cooling, some iceis added, and the receptacle is also outwardly cooled with ice. Afterthe mixture is well cooled, a solution of 4 parts by weight of sodiumnitrite in 16 parts by volume of water, is slowly added with rigorousstirring. The temperature should be maintained at approximately 4 C. andit is advisable to add from time to time some ice to the mix. Thestirring is continued, maintaining the temperature below 4 C. for atleast 15 minutes, whereupon this diazo suspension, being constantly keptcool,

is gradually added with rigorous stirring to a solution of 9.2 parts byweight of p naphtol dissolved in "165 parts by volume of a 2n. NaOHsolution. Afterthe last portion of the azo suspension has been added,the stirring of the now 40 brown-red coupling solution is continued fora period of from /2 to 1 hour. After filtration and thorough washing,the resulting product is of g a fine orange shade, and 01' fibroustexture.

Instead of the cellulose p-nitro-benzoic acid 45 ester, I may use thecellulose p-nitro benzyl ether, and convert the same into the azodyestufi. in substantially the same manner as described in the foregoingexample. In most cases the stability of the ether compounds is evengreater 50 than that oi. the ester dyestuffs. The reaction, furthermore,is not limited to p-nitro compounds, but also ortho and meta nitrosubstances may be used. The same result is obtained by substituting theester or ether used in the above example 55 by a mixed ester or ether,such as cellulose acetate-nitro benzoate, cellulose nitrate-nitrobenzoate, cellulose ethyl ether-nitro benzoate, cellulose acetate-nitrobenzyl ether, cellulose nitrate-nitro benzyl ether, cellulose ethylether- 60 nitro benzyl ether, and the homologues 01' such and similarsubstances, substantially as represented by and expressed in theabove-recited generic formulae. .The color produced by all these isusually substantially the same as that 65 of the straight esters orethers, though in some instances a bathochrome or hypsochrome efiect isobtained, due to the presence of groups characteristic for producingsuch effects. As a general rule, however, this bathochrome or hypso- 70chrome effect is not very pronounced, due to the fact that these groupsare not in direct combination with the carrier molecule of the chromo--phgre. gm 1p on groups, but are esterifled or etherifled with thecellulose, and can, therefore,

75 exercise their influence only indirectly. ,Nat-

urally, the introduction of bathochrome or chromophore groups directlyinto the carrier molecule of the chromophore group or groups, willeffect a change or modification of the color. The introduction of, forinstance, a second azo group, as illustrated in Example 5, isrepresentative of such a procedure and is within the purview of myinvention.

The nitro esters or ethers that may be used in accordance with theinvention are easily obtained by the commonly used methods foresterifying or etherifying cellulose or cellulose derivatives, forexample, by treating alkali cellulose or partly esterified or etherifiedalkali cellulose with a nitro aromatic acid chloride or a nitro aralkylchloride or with an aromatic acid chloride, or an aralkyl chloride, andsubsequently nitrating the ester or ether obtained. The nitration in thelatter instance may be effected either in a solution of the ester orether in an organic solvent inert to aromatic nitration, or in asuspension of the ester or ether. Where a suspension of the ester orether is nitrated, which is necessary it the ester or ether is butdifilcultly soluble in the usual commercial solvents, care must be takenthat the suspension is as fine as possible. I have found it of advantageto proceed in the followiiig manner: 22 parts by weight I of thecellulose ester or ether are treated on a water bath of 70 C. for 7hours with rigorous stirring, with 500 parts by volume of a nitrating 1solution (346 parts by volume concentrated HzSOl+305 parts by volumeconcentrated HNOs).

a large amount of water, whereupon the product is permitted to settle;after decantation and washing, the nitro product is separated byfiltration and thoroughly washed. In every case of esterification oretherification it is of advan 'tage to add as a catalyst a slight amountof the metal halide to be separated during the esteriflcation oretheriflcation process.

Sometimes when the H of the OH group of the glucose residue of thecellulose molecule to be esterified is activated by the presence ofcertain activating groups such as the nitro, acetyl and similar groups,it is not necessary to use a cellulose metal compound. In the case, forinstance, of cellulose dinitrate or diacetate, the esterification willsmoothly proceed with the acid chloride in the presence or a suitablecatalyst, such as P015 and like substances, with evolution of HCl. If,in addition, the C1 of the acid chloride is activated by the presence ofactivating groups. such as COOH, N02, etc., the reaction will evenproceed without such catalyst, as illustrated by Example 6.- Sometimesit is advisable to use the aralkyl bromide or the aromatic acid bromidefor the etheriflcation or esterification.

Example 2.-2 parts by weight of the cellulose amino ester produced asdescribed in Example 1, is treated with 10 parts by volume of a dilutedsulphuric acid (of the same strength as used in Example 1) and heated ona water bath of a bath temperature of 70 C; from 15 to 30 minutes. Altercooling and adding ice to the mix, as well as outwardly cooling thereceptacle, a solution of 2 parts by weight of sodium nitrite in 8 partsby volume of water is slowly added with rigorous stirring to the mix,maintaining the temperature at 4 C. The stirring is continued,maintaining the temperature below 4 C. for at least another hour afterthe last portion of the nitrite has been added. The diazo suspension,

After the mixture has cooled down, it is added to r being constantlykept cool, is then gradually ided to a rigorously stirred solution of4.1 parts by weight of H" acid (the term commonly used for4-amino-5-hydroxy-2, 'l-naphthalene disulphonic acid) in 5'? parts byvolume of a 2n. NaOH. After'all of the diazo suspensio s has been added,the stirring is continued for at least one hour, whereby the color ofthe solution turns gradually a dark purple. The resulting product, afterfiltration and thorough washing, is of a lilac color and possesses'rfibrous texture.

Eramplei-Z parts by weight of the amino ester or ether obtained asoutlined in Example 1, is heated with sulphuric acid, thereafter cooledand diazotized in the manner specified in Example 1. The diazosuspension is gradually added to a rigorously stirred solution of 2.7parts by weight. of salycilic acid in 9.5 parts by weight of sodadissolved in 40 parts by volume of water. The stirring is continued forat least one hour, the solution turning gradually dark yellow. Afterfiltering and washing, the resulting product is a fine yellow color andof fibrous texture.

Example 4.-2 parts by weight of the amino ester or ether diazotized asrecited in Example 1, is gradually added while constantly kept cool, toa vigorously stirred solution of 5.6 parts by weight of R salt in asolution of 7 parts by weight of soda (Na2CO3+1H2O) in 82 parts by,volume of water. The stirring is continued for at least one hour. Theresulting product, after filtration and thorough washing, is of a finered shade and possesses a fibrous texture.

Example 5.--4.1 parts by weight of .H acid are dissolved in a solutionof 3 parts by weight of soda (NazCOs-I-lHzO) in 35 parts by volume ofwater add more soda if necessary until reaction is alkali). ice and adiluted 'HCl solution is added until a slightly acid reaction(Congo'paper) is obtained. A diazo solution of 2.1 parts by weight ofpnitranilin is prepared by dissolving the same in 5.5 parts by volume ofa diluted HCl (15 parts by volume of concentrated HCl+20 parts by volumeof water) and adding the same rapidly to a mixture comprising 45' partsby weight of ice, 30

parts by volume or water, 1.5 parts by volume of concentrated HCl and7.6 parts by volume of a sodium nitrite solution (1.4 parts by weightsodium nitrite in 10 parts by volume of water).-

The diazotized nitranilin solution is then gradually added to therigorously stirred solution of "H" acid- Stirring is continued foronehour and during this period, preferably after /2 hour, a diluted acetatesolution is carefully added to buffer the prevailing acidity. After thereaction is completed, the solution having acquired a dark red color, somuch soda is added that a slightly j alkaline reaction is obtained. Anadditional 7 parts by weight of soda are then added to the mix to insurealkalinity during the subsequent coupling. A diazo suspension producedfrom 2 parts by weight of the amino ester or ether, prepared asdescribed in Example 1, is then gradually added to the rigorouslystirred coupling solution.

. The stirring is continued for a period of from 1% to 2 /2 hours. Theresulting product, after filtration and thorough washing, is of a darkblue color and possesses a fibrous texture.

Example 6.-12.6 parts by weight of a cellulose dinit'rate (approximately11% 'N) in a solution of 130 parts by weight of 'amyl acetate areadmixed with 8 parts by weight of p-nitro-benzoic acid -dissolved hot in150 parts by volume of ethyl acetate. The mixture is well stirred untilsubstantially all of the acid is dissolved. .155

The solution is admixed with parts by weight of thionyl chloride arethen gradually added with continuous stirring. Suflicient P015 to assistthe liberation of HCl is added as a catalyst. Alter the last portion ofthe thionyl chloride has been added, the stirring is continued on awater bath for 'a period of from 2 /2 to 3 hours. Care should be takenthat no moisture enters the receptacle during the reaction. It. is ofadvantage to provide the reflux condenser with a drying tube filled withfused calcium chloride. For the same purpose it is advisable to use aseal for the stirrer. After the reaction is completed, the mix is addedin a fine stream to a large amount of vigorously stirred cooled water.After filtering and thorough washing, the product is dried, andextracted with alcohol in order to remove unesterified nitrobenzoicacid; The cellulose nitrate-nitro-benzoate is insoluble'in alcohol. Thenitro ester is then reduced, treated with acid to form the amino salt,and diazotized as described in Example 1. The diazo product may then becoupled with any one of the coupling agents mentioned in Examples 1 to5, or with any other suitable coupling agent. v The derivatives of thepartly nitrated and/or. acetylated celluloses have the advantage thatthey are more easily soluble in many of the commonly used organicsolvents than other cellulose. derivatives, such as, for instances, thestraight benzoates, and particularly the di- 'ber'izoates.

'In the foregoing example, instead of the pnitro-benzoic acid, thep-nitro benzoic acid anhydride may be'used, in which case the presenceof the catalyst (PCls) may be dispensed with. The reaction proceeds evenmore smoothly with p-nitro-phthalic acid anhydride or a mono ester ofp-nitro-phthalic acid, such as, for instance,

the p-nitro-phthalic 1 acid monobutyl' ester. Here again the nitroproducts may be also obtained by nitration, subsequent to theesterification with the plain anhydrides or acids or acid esters.

Instead of ,diazotizing the cellulose amino derivative and coupling thesame with a suitable coupling agent, it is possible and may be sometimesof advantage to follow a different procedurel The cellulose molecule insuch cases may be. esterified or'etherified with an aromatic system thatis ordinarily a coupling medium for diazotized substances. Thecellulose, for instance, may be esterified with salycilic acid, and maythen be treated with a diazo solution of, for instance,- P-nitranilin.In a like manner it is possible to connect the cellulose in ether orester combination with an a and 3 naphthyl carboxylic acid and similarsubstances.

In all the examples care should be taken that the salt formation of theamino ester or ether prior to the diazotation is as complete aspossible. The finer the individual particles of the amino compound are,the better will the salt formation proceed. Dependent on the fineness ofthe particles, it may be necessary to, heat the amino times difllcult toobtain, and in many cases,

despite higher concentrations and prolonged heating, the chlorideformation is incomplete and unsatisfactory. It is preferred, therefore,to use sulphuric acid for the salt formation of the amino compound.

'It should be observed that in each case the time within which thediazotation is completed is primarily dependent upon the particlefineness of the amino salt. It is sometimes necessary to continue thestirring, maintaining the temperature below 4 C., after the addition ofthe nitrite solution, for an additional 5 to 30 minutes and more ifnecessary, to insure proper and complete diazotation.

The same considerations are true for the coupling reaction. In thisinstance, however, the time within which the coupling is completed isnot only dependent upon the particle fineness of the diazo suspension,but also to a considerable extent upon the nature of the coupling agent.Some media will couple better than others, and it is generally necessaryto continue the stirring of the coupling mixture for at least 15 minutesafter all of the diazo suspension has been added. In many instances thestirring must be continued for a period of 2 hours or even more, untilthe coupling reaction is completed.

In all cases where, for eii'ective coupling, an alkaline condition isrequisite, it is necessary to add sumcient alkali, either in the form ofalkali hydroxide, or alkali carbonate to the coupling solution, to takecare of the acid added with the diazotate and to maintain at all timesan alkaline reaction. Naturally, where it is essential that the couplingbe effected under acid conditions, care should be taken that thecoupling solution is slightly acid or at leastneutral. In such cases itis of advantage to add a slight amount of an acetate solution to bufferthe acid introduced with the diazo solution, for, if the acidity is toohigh, the coupling will proceed, but unsatisfactorily.

It is understood that where the intermediary products with which thevarious reactions are carried out are soluble in a particular solvent,it is possible and frequently of advantage, to carry out the variousreactions in solution.

It is within the scope of my invention to substitute polynitro compoundsfor the mononitro compounds hereinabove referred to, and particularizedin the examples, and to obtain thereby cellulose polyazo dyestuffs.

Inasmuch as the presence of an auxochrome group is an essentialpre-requisite in conjunction with a chromophore group for any dyestuif,it is understood that such auxochrome groups are present in the productsobtained in accordance with the invention. They may be either alreadypresent in the aromatic carbocyclic acid radical,

or the carbocyclic aralkyl with which the cellulose molecule isesterified or etherifled, or they may be introduced as a constituentpart of the coupling agent, or else may be introduced by a subsequenttreatment (1. e., sulphonation). It will be noted that the dyestuflsobtained by the afore-mentioned examples possess such auxochrome groupsas, for instance, OH, SOaH. Where, howeventhe colored products aremerely used as pigments, and where their fixation upon a fiber orfibrous material is not contemplated, as,for instance, in theirapplication as pigments for varnishes, lacquers and the like, suchauxochrome groups need not be present.

Wherever the term "cellulose molecule" appears in the specification andclaims, it is used in its broadest sense, and includes the cellulosemolecule as such, as well as the residue of a cellulose molecule, amolecule of a cellulose derivative, such as esters, ethers, mixedesters, mixed ethers, ester ethers, and the residue of such cellulosederivative molecules.

I claim:-

1. A new dyestufi consisting substantially essentially of a coloredcellulosic material of the general formula in which Z represents aradical of a member of the cellulose group consisting of cellulose,cellulose esters, cellulose ethers, cellulose mixed esters, cellulosemixed ethers and cellulose esters ethers, R at least one radical of anaromatic compound, R a radical of a member of the group consisting ofaliphatic alcohols and aliphatic acids, R any aromatic system, m thenumber of azo groups carried by R :1: the number of linkages of R to Z,m and :1: being at least one in number for every glucose radical of Z,and at least one member of the group consisting of R R and R carrying atleast one auxochrome group.

2. A new dyestuif in accordance with claim 1 in which R is a radical ofan aliphatic alcohol in ether combination with at least one of the OHgroups of Z per glucose radical and in which said auxochrome group iscarried by at least one member of the group consisting of R. andR 3. Anew dyestufi' in accordance with claim 1 in which R is a radical of analiphatic acid in ester combination with at least one of the OH groupsof Z per glucose radical and in which said auxochrome group is carriedby at least one member of the group consisting of R and R '4. A newdyestuif consisting substantially essentially of a colored cellulosicmaterial of the general formula groups of Z per glucose radical, R anyaro-.

matic system, 111. the number of azo groups carried by said aromaticacid, a: the number of ester linkages of-R R to Z, m and a: being atleast one in number for every glucose radical of Z, and at least onemember of the group consisting of-R -R and R carrying at least oneauxochrome group.

5. A new dyestufi in accordance with claim 4 in which said auxochromegroup is carried by- R R 6. A new dyestufi in accordance with claim 4 inwhich said auxochrome group is carried by R 7. A new dyestufi consistingsubstantially essentially of a colored cellulosic material of thegeneral formula Z[R R },-{N N -R in which Z represents a radical of amember of the cellulose group consisting of cellulose, cellulose esters,cellulose ethers, cellulose mixed esters, cellulose mixed ethers andcellulose esters ethers,-R R a radical of an aromatic alcohol in ethercombination with at least one of the OH groups of Z per glucose radical,R any aromatic system, m the number of azo groups carried by saidaromatic alcohol, a: the number of ether linkages of-R'R-"to Z, m and a:

being at least one in number for every glucose radical of Z, and atleast one member of the group consisting of-Rfi-Rfi-and R carrying atleast one auxochrome group.

8..A new dyestuif in accordance with claim 7 in which said auxochromegroup is carried byR*--R 9. A new dyestuff in accordance with claim 7 inwhich said auxochrome group is'carried by RP.

10. A process for the manufacture of new dyestuffs which comprisesreducing a cellulosic material consisting substantially essentially of acellulose derivative of the general formula in which Z represents aradical of a member of the cellulose group consisting of cellulose,cellulose esters, cellulose ethers, cellulose mixed esters, cellulosemixed ethers and celluloseesters ethers, R at least one radical ofan'aromatic compound, R a radical of a member of the group consisting ofaliphatic alcohols and aliphatic acids, m the number of nitro groupscarried by R and a: the number of linkages of R to Z, 11!. and :c beingat least one in number for every glusoce radical of Z, then treatingwith acid to form an amino salt, thereafter diazotizing said salt andcoupling the diazotate with a suitable coupling agent, said couplingagent and said cellulose derivative being, so selected that at least oneof themcarriesat least one auxochrome group.

11. Process in, accordance with'claim in which a suspension of said saltis diazotized and coupled.

12. A process for the manufacture of new dyestuffs whichcomprisesnitrating a suspension lof a cellulosic material consistingsubstantially essentially of a' cellulose derivative of the general inwhich Z represents a radical of -a. member of Z, reducing the nitroproduct obtained, then treating with an acid to form an amino salt,thereafter diazotizing said salt and coupling the diazotate with asuitable couplingagent, said coupling agent and said cellulosederivative being so selected that at least one of them carries at leastone auxochrome group.

13. A process for the manufacture of new dyestuffs which comprisesesterifying a cellulose material with a sufficient amount of an aromaticacid of the general formula hi -Ii. in which R. is a radical of anaromatic compound capable of coupling with a diazotate and R a radicalof an aliphatic acid, to thereby form a product consisting substantiallyessentially of a cellulose ester containing -at leastone aromatic acidradical for every glucose radical present and coupling said ester with adiazotate, said aromatic acid and said diazotate being so selected thatat least one of them carries at least one auxochrome group.

14. A process for the manufacture of new dyestuifs which comprisesetherifying a cellulose material with a suflicient amount of an aralkylalcohol of the general formula lie-R in which R is a radical of anaromatic compound capable of coupling with a diazotate and R a radicalof an alkyl alcohol to thereby form a product consisting substantiallyessentially of a cellulose ether containing at least one aralkyl radicalfor every glucose radical present and coupling said ether with adiazotate, said aralkyl alcohol andsaid diazotate being so selected thatat least one of them carries at least one auxochrome group.

15., Alprocess for the manufacture of new dyestuffs comprising reducinga cellulosic material consisting substantially essentially of acellulose nitro-benzoate, then treating with acid to form an amino salt,thereafter diazotizing said salt and couplingthe diazotate with asuitable coupling'agent'carrying at least one auxochrome r p- 16. Aprocess for the manufacture of new dyestuffs which comprises reducing acellulosic material consisting substantially essentially of a cellulosenitrobenzyl ether, then treating with acid to form an amino salt,thereafter diazotizing said salt and coupling the diazotate with asuitable coupling agent carrying at least one auxochrome group.

RALPH DINKLAGE.

